It has been widely known that electronic parts such as LSIs and IC chips produce heat during use, and that their performances will thus be impaired due to such heat. Various heat dissipation techniques have been employed to solve this problem. For example, there is known a technique of disposing a cooling member such as a heat sink in the vicinity of a heat-emitting portion, and then allowing the two to come into close contact with each other so as to facilitate an efficient heat transmission from the heat-emitting portion to the cooling member, thereby allowing the heat of the heat-emitting portion to be efficiently dissipated. At that time, air which has a lower thermal conductivity resides in any gap between the heat-emitting portion and the cooling member such that heat transmission will become inefficient, and that the temperature of the heat-emitting portion will thus fail to decrease sufficiently. In order to avoid this phenomenon, there have been used heat dissipation materials having favorable thermal conductivities and conformable surfaces, such as a heat dissipation sheet and a heat dissipation grease (Patent documents 1 to 3), for the purpose of preventing air from residing in between the heat-emitting portion and the cooling member. Particularly, heat dissipation greases exhibit high performances in terms of heat resistance, since they can be used in a thinner form in a package.
Also, in order to further improve the heat dissipation property, there has been studied a technique of reducing thermal resistance by making a heat dissipation grease used in a package thinner and improving the thermal conductivity of the heat dissipation grease itself (Patent document 4).